Tunnel kiln and method of operating same



Aug, w, 1924.' N y 1,505,768 P. DH. DRESSLER I TUNNEL KILN AND METHOD OF/OPERATING SAME Filed my 2e 1923 s sheets-sheet l i r-l/' Aug. 19, 1924. i 1,505,768i

P. D H. DRESSLER TUNNEL KILN AND METHOD OF OPERATING SAME Fild July 26. 1923 :s sheets-sheet 2 mnu ATTORNEY F. DH. DRESSLER TUNNEL KILN AND METHOD OF OPERATING SAME Filed July 2e. 1.923 s sheets-sheet C) it' INVENTOR Patente Aug. 19, 1924.

STATES y l 1,505,768 PATENT oFFlcE.-

PHILIP DIIUC DREssLEE, OE CLEVELAND, OHIO, AssIGNon Tol AMERICAN DnEssLEn TUNNEL xILNs, INC., or CLEVELAND, OHIO, A CORPORATION OE NEW YORK TUNNEL KILN AND METHOD OE OPERATING.v sAIm Application filed Ju1y'26, 1923. Serial No. 653,892.

To all whom it may concer/n.:

Be it known that I, PHILIP DIIUO DRESS- LER, a subject of the King of Great Britain, and resident of Cleveland, in the county of Cuyahoga and State of Ohio, have invented certain new and useful Improvements in Tunnel Kilns and Methods of Operating Same, of^ which the following is a specification. l o

My present invention relates to continuous tunnel kilns, and the general object of the invention is to make provisions for the maintenance 'of cer-tain temperature conditions in the kiln which are especially desirable in annealing malleable castings.

Ordinarily in annealing malleable castings, it is desirable to heat'the castings as rapidly as possible up to a ,certain maximum temperature and to hold them in their high ly heated condition and without appreciable temperature change during a soaking period of many hours duration. The -castngs should then be cooled downto a temperature some. hundreds of degrees below the maxiA mum temperature and maintained without further cooling or only slight coolingfor another considerable period of time comparable in duration with, though usually somewhat shorter than, the initial soaking period, after which the castings are cooled down to the temperature oi emergence. The initial and final cooling of the castings/)may be car ried out rapidly without injury to the cast ings, and it is always desirable, of course, to make the cooling as -rapid as possible .since a shortening of the cooling period shortens and cheapens the construction cost of the,

kiln required for a given output.

In constructing a kiln in accordance with the present invention, I interpose a slow cooling or low temperature soaking zone between initial and final cooling sections of the kiln, and provide means for supplying heat to` said interposed Zone to prevent 'the ware therein from being cooled asyit otherwise would, as a result of radiation romfthel outer walls of this portion ofV the kiln ione and the unavoidable circulation'of the kiln atmosphere. The heating means which I thus add to the kiln are preferably regulable to vary the temperature conditions maintained in response to the requirements of service without interfering with the proper operation and regulation of the main kiln heating means. l

The various features of novelty which clfialfacterize'myA invention are, pointed out with particularity in the claims yannexed to and forming apart of this specification. For a better understanding of theinvention,

advantages, yreference however, and its should be had to the accompanying draw- Fig. 2;

Fig. 6 is a diagrammatic plan view partly in section of a muilie heated kiln;

Fig. 7 is a longitudinal section of the kiln shown in Fig. 6;

Fig. 8 is a'transverse section of the kiln shown in Fig. 6;

Fig. 9 is a temperature curve;

Fig. 10 is a partial plan section of a modified form of the kiln shown in Figs. 6, 7, and 8;

Fig. 11 is a partial section of the kiln shown in Fig. l0; and Fig. 12 is a view sim- /ilar to Fig. l illustratinganother modification.

Figs. l to 5 of the drawings show an open ire kiln A especially adapted to cause the malleable 'castings or other ware passing through the kiln to vary in temperature at diierent points along theI lengthof the kiln in general accordance with the temperature curve tof Fig. 3. The kiln may be re arded as comprising a heating up an hig tem' perature soaking zone a, an initial cooling Zone b, a slow cooling or low temperature soaking zone o, and a rapid cooling zone d. The zone a of the kiln may be constructed and heated in any of the usual or suitable preferred embodiy ways employed in open lire kilns in which nos' gasbs. from the fire boxes B are withdrawn from the kiln chamber proper at the entrance end of the latter through an outlet C connected to a suitable draft creating device.

As shown there are two such draft creating be connected by proper manipulation of the dampers Dand D.

The kiln zone Z7 is provided with coohng means which may be of any of the known lor suitable forms for cooling a portion of an open fire tunnel kiln in which the kiln temperatures are analogous l ,kiln disclosed. As vshown the zone b y1s cooled'by admitting a gaseous med1um to the kiln chamber through ports Gr opening to the kiln chamber from vertical channels H formed in the side walls of the kiln chamber. These channels are connected at theirl lower ends to longitudinal channels l, one at each side of the kiln. The connection between each vertical channel H and theocrres onding flue I is controlled by an individiial damper D2. The' two lues l are both connected to a transverse'ue l running v under the kiln. As shown, the flue J vis connected by a pipe or conduit F to the outlet from the exhaust fan F, which thus supplies warm products of combustion to the lues H, and through the ports G to the interior of the kiln chamber in the zone b. ln addition to the regulation of the cooling effect in the zone b obtainable by manipulation of the various dampers D2, the ports G may be independently adjusted, as by placing throttle vbrick Gr of different to permit the insertion, removal and adjust.- ment of the throttle brick G', openings K, normally closed by suitable plugs o-r closing devices K', are formed in the outer walls of the channels H.

Means are provided for supplying heat as required to the kiln zone c. e means shown for this purpose comprise iire boxes B at each side of the kiln zone c, in proximity to the junction of -that zone with the coollng zone b.v The heating gases from the fire boxes B are Iwithdrawn from the kiln chamber at the end of the zone c adjacent the rapid cooling zone d, by suitable connections to a draftcreating device such as the stack L. As shown, the connections between the kiln chamber and the stack L comprise vertical lues M in the side walls of the kiln chamber which are distributed along'v a portlon of the length of the kiln, and communicate with the-interior of the 4kiln chamber through-ports N. The ilues Min each side wall-of the kiln, are connected at their lower ends to acorresponding longitudinal flue O, the connection between each vertical flue M and the corresponding iiue O being regulated by a damper D3. The two iues O are connected to the stack L by a. cross iue P,

to' those in ther sizes in the ports, andl To permit the ports N to be regulated by throttle brick, openings M normally closed by suitable plugs Vor closing devicesv are formed in the outer walls of the iues M.v

be cooled in any usual or suitable manner for effecting rapid nal cooling in an open fire kiln. 'As shown the ,cooling provisions for the Zone d comprise a bank of metal,

` pipes Q at each side of this portion of the -R running to a suitable draft creating device shown as a fan S. The hotv air delivered by the fan S may be used in any way in which air heated by a tunnel kiln is normally used, as in heating, drying, or supplying preheated air of combustion to the lire boxes B and, B. l

As shown the kiln A is provided at its entrance and exit ends with an ante-chamber A and an exit chamber 4A2, respectively. The -chambers A and -A2 may be separated from the kiln chamber-proper, by doors T. and are normally closed from the atmosphere at their outer ends by doors T. Where it is desirable to avoid oxidizing conditions in the kiln chamber, the influx of air into the kiln chamber when either door T is open may be prevented by supplying a neutral gas to. the ante and exit chambers either constantly, or whenever necessary to prevent the passa e of air from those chambers into the iln c amber proper. For this purpose valved branch pipes F2 and F3 run from the conduit F to the chambers A and A.

With the kiln construction described it is readily possible tol cause the ware to vary in temperature 'as it progresses through the kiln in the manner indicated by the temperature curve t of Fig- 3. The described provisions for imparting heat to the slow cooling or low temperature soaking zone C, make it readily possible to hold the temperature of lthe wareconstant between the points 1 and 2 'on the curve, and .to shift either or both of these points longitudinally of the kiln. To secure-the last mentioned result I .vary the relative rates at which heat is supplied to the kiln chamber from the different fire boxes B at each side of the kiln, and vary the relative amounts of heating gases taken oil' through the different tubes M.

With the means shown for heating the Zones a and c, itis possible to cool the initial cooling zone b by introducing a cooling gaseous medium directly into the kiln chamber without interfering with the operation of the heating means at either end of that zone. As far as the cooling ei'ect inthe zone b is concerned, it is immaterial whether the cool- The rapid cooling zone d of thexkiln may henares If air is used there would be an oxidizing eEect objectionable in some cases which is avoided by the use of products of combustion as Ithe cooling agent. The preheating of the cooling agent suppliedto theyzone b, reduces the risk of undulyrapid local cooling and facilitates close regulation of the temperature in this zone of the kiln. When it is neither necessary to use a heated cooling agent nor to avoid the use of a cooling agent having an oxidizing effect, the damper D4 may be closed and the damfper DE opened, tol

thereby disconnect the flue J from the outlet from the blower F and connect it through the outlet J to the atmosphere, so that at- -v mospheric air will then be drawn into the kiln chamber through the dues H and ports G. I' y ln Figs. 6, 7, and 8, ll have illustrated a kiln AA having muflle heating provisions, and in which the Ware passing through the kiln may be subjected to the temperature variations indicated in-Fig. 3. 'In the kiln AA heat is supplied to the'heating up and high temperature zone a of the kiln by combustion chambersU located in the kiln chainber, one at each side of the goods pathway therethrough, andl each extending the full length of the zone a. The combustionj chambers U illustrated are of the type commonly employed in Dressler tunnel kilns, the Walls of each combustion chamber being formed of sections of tile extending transversely to the length of the kiln and formed With open ended channels U which unite to forni `a ue plied to eachcombustion chamber U through l burner nozzles W distributed along the high temperature end ofthe zone a. Products of combustion are Withdrawn from each combustion chamber U through an outlet port U2 at lthe entrance end of the kiln, and; a conduit CA by which both ports U2 are oonnec'ted to a suitable draft crean'ng device.

As shown the draft Creating device eInployed is a fan FA which draws the heating y'gases from the conduit @A through the hot gas passages of a recuperator X, and discharges them partly to an outlet stack "EA,

and partly to the pipes F2 and F? supplying products fof combustion to the kiln ante and exit chamber A and A2, respectively. Fuel in the form of oil orgas is supplied to each of the burner nozzles W through a separate valved connection W from fuel `supply pip'- ing W2. Air for the combustion of thefuel is blown through the recuperatnr X,V and preheated therein, by a fan Y, and is delivvvith each of the chambers U and between the latter and the exit end of the kiln. The combustion chamber extends along the full length of the zone c of the kiln and through most of the length of the zone b. The combustion chambers UA are provided With burner nozzles WA similar tothe nozzles W, and each having separate valved connections W and X to the fuel and air supply pipings W2 and X2, respectively. Preferably as shown each combustion chamber UA is provided with a plurality of nozzles WA distributed along the length of a por-` tion of the combustion chamber UA adjacent the corresponding combustion chamber U. Products of' combustion are vvithdravvn` from the combustion chambers UA by. means of a suitable draft creating devis?J shown as a stack LA lwhich is connected to the ends of the combustion ychambers UA adjacent the exit end of the kiln by a suitable port and conduit arrangement. The

final cooling (zone d of the kiln AA may `be and is shown as being exactly like the iinal cooling zone d of the kiln A.

ln operation, by suitably regulating the valve fuel and air supply connections W and X td the different burner nozzles WA, temperature conditions in the zones and c of the kiln maybe varied to suit the conditions of operation. To cause the Ware to lvary' in temperature as indicated by the temperature curve of Fig. 3 "in passing through the zones b and c of the kiln AA, air but not fuel is supplied to one orinore of 'the burner nozzles WA of each combus tion chamber UA adjacent the zone a of the kiln, While fuel, and any additional air Vrequired for its combustion, is supplied to the burner nozzles WA nearer the exit end of the kiln. The air thus supplied to some of4 the burner nozzles WA Without a corresponding supply of fuel thereto, actsas a cooling agentV supplementing the 'external radiation from the kiln in effecting a com paratively rapid cooling ofthe Ware passing through the corresponding portion of the kiln.- By supplying both fuel and air for its\ combustion in suitable amounts to the burner nozzles WA adjacent the zone a, l

chambers UA are located Wholly vvithin the i zone a of the kiln, and the Width of the kiln is contracted in the zone b and the cooling nov . With thisV arrangement the flues Z act like ltunnel kiln comprising a heating up Zone' at 'one end, and a final cooling Zone at the oppoilues Z are formed in the side walls of this portion of the kiln. The lines Z communicate with the atmosphere through ports Z. adjacent the ground level, and at their upper ends the iiues Z open into la charhber Z2 in the-roof of the kiln chamber proper and provided with suitable valved outlets Z3.

chimneysv to' move atmospheric air upward through them and thus add to the natural radiation loss of heat in this portion of the kiln chamber. The modification illustrated in Figs. and 11 is well adapted for causing the Ware passing through the kiln zones b and c to vary -in temperature according tow the temperature curve t shown in Fig. 3.

In Fig. 12, I have shown an. open kiln diiferingfrom that shown in Figs. vl, 2` 4 and 5 in that the blower/F and conduits F', F2 and F 3, and the stack L, and the flues M are omitted, and a stack LA is connected to the kiln chamber through a damper con? trolled conduit CA, which communicates with the kiln chamber at points intermediate theA ues H and combustion chambers B.

With the stack L replaced in effect bythe` stack LA the direction of :gas fiow through the slow cooling Zone of the kiln is reversedg but in a general way the same temperature conditions can be maintained as in the kiln shown in Fig. l. y

AThe omission of the blower F and conduits F, F2 and F3 simplifies the .kiln construction and is therefore desirable incases in which the kiln chamber atmosphere con- .trol obtainable with them is unnecessary.

The use or non use ofthe blower F and co'nf duits F', F2, andy F3 obviously does not depend on whether the stack of Fig. l, or the g stack vLA 'of Fig. 12 is employed. Y

Certain novel features of my invention specificA to the embodiments illustrated in Figs. 7, 8, 10, l1 and 12, as distinguished from 'Figs l, 2,3, and 5, are not claimed herein, `but are claimed in my prior application', Serial No. 394,985, in which claims are also made on the provisions shown, but not claimed herein for introducing products of combustion into the tkiln antechamber and exit chamber.

While in accordance with theprovisions of ythe statutes,l have illustrated and d escribed the best `forms oimy invention, now

known to ine, it will be apparentto those" skilled in the art that many changes lin C form may be made Without` departing from the spirit of my invention, and that certain ifea-y tures of my invention may sometimes be employed to advantage without a corresponding-Iuse of other features.

. aving now described my invention, what Iclaim as'new and desire to secure by Letters Patent, is: l

1. The method of operating a tunnel kiln which consists in maintaining' a high temsite end of an intermediate portion of the kiln, which4 consists in causing a heating l fluid to flow through the heating zone and a cooling fluid to flow through the cooling zone, each in a direction opposite to thatin which the goods pass through the kiln, and

in causing a heating fluid to flow in the opposite direction through the intermediate portion of the kiln.

3. The method of operating a tunnel kiln which consists in supplying heating gases to the kiln at the opposite ends of an inter-v mediate section of the kiln and moving the.

heating vgases so supplied away from said intermediate -section toward the oppositeends of the kiln chamber.y

4. The method of operating' an open fired tunnelkiln which consists in supplying heating gases to the kiln chamber at the opposite ends .of an intermediate section of the kiln chamber and vmoving the heating gases' so supplied through'the kiln chamber awajy7 from said intermediate section toward the opposite ends of the kiln chamber.V

5. The method of operatinglan open fired tunnel kilnl -which consists in supplying heating gases to the kiln chamber at the opposite ends ofan intermediate section of the kiln chamber and moving the heating gases so supplied through the kiln chamber away Jfrom said intermediate section and toward the ends intermediate section of the kiln chamber at a temperature vappreciably above the temperature of the atmosphere and appreciably' kiln chamber and returning a portion of the of the kiln chamber and introducing products of combustion into saidvheating gases leaving' the kiln chamber to a cooling zone section of the kiln chamber at a temperature appreciably above that of they atmosphere but below that existing in the portion of the 'kiln chamber into which `i the gases are returned.

tunnel kiln lwhich consists in maintaining f7. The methodfof operating an openjiire av heating up and high temperature soaking zone, an initial cooling zone and a slow co lng or low temperature soaking zone 1n the ends offthe kiln, by introducing heating order stated between the entrance and exit C momes' gases into the first and third mentioned zones and introducing a gaseous cooling a heating up and high temperature soaking Zone, an initial cooling zone and a slow cooling or vlow temperature soaking zone in the order stated between the entrance and exit ends of the kiln by introducing a gaseous cooling medium into the rapid cooling Zone portionk of the kiln chamber and supplying heating gases to the kiln chamber in each of the other of said Zones and withdrawing the heating gases so supplied from the kiln which consists in provisions for cooling av sectionof the kiln chamber immediately adjacent the high temperature Zone of the kiln.

and between said zone and the exit end of the kiln with comparativel rapidity and means for supplying heat to a second section of the kiln between the iirst'mentioned section and the exit end ott the kiln.

10. In an open fire tunnel kiln having provisions for supplying heating gasesy to, and moving them through the high' temperature zone of the kiln chamber toward the entrance end of the latter, the improvement which consists in means for maintaining a slow cooling zone in the kiln chamber between the high temperature Zone and the exit end of the kiln, and means for maintaining an initial cooling zone in the kiln between the slow cooling and high temperature zones.

11. ln an open -red tunnel kiln, provisions 'or maintaining a high temperatureand heating up zone adjacent the entrance end of the kiln, and an initial cooling zone adjacent the high temperature zone and between it and the exit end of the kiln, and a slow cooling zone between the rapid cooling Zone andthe exit end of the kiln, comprising means for lsupplying heating gases to the kiln chamber at the end of the high temperature zone remote from the entrance end cgt the-kiln and for withdrawing said gases from the kiln at a point less remote from said entrance. end, and .means for supplying heating gases to the kiln chamber adjacent.

the end of the slow cooling zone remote from the exit end of the kiln and for withdrawing the last mentioned gases from the kiln at a point less remote from the exit end of the kiln.

12., ln an open re tunnel kiln having provisions for supplying heatin gases to and moving them through the hig temperature zone oit the kiln chamber toward the entrance end of the latter, the improvement which consists in means for retarding the cooling of the ware in a portion of the kiln chamber-between the high temperature zone and the exit end of the\kiln,'compris ing provisions for supplying heating gases `to the kiln chamber at the end of said portion remote from the eXit end of the kiln and for moving the last mentioned heating gases through the kiln chamber toward the exit end of the latter.

18. In an open fired tunnel kiln, provisions for maintaining a high temperature I andY heating up zone adjacent the entrance end of the kiln, and an initial cooling zone adjacent the high temperature zone andbetween it and the exit end of the kiln, and a slow cooling zone between the rapid cooling zone and the exit end of the Zone, comprising means for supplying heating 'gases to the kiln chamber at the end of the high temperature -zone remote from the entrance end of the kiln and for withdrawing said gases from the kiln at a point less remote from said entrance end, and means for .supplying heating "gases to the kiln chamber adjacent the end of the Slow cooling Zone remote from the exit end of the kiln and for withdrawing the last mentioned gases from the kiln at a point less remote from the exit end of the kiln, and meansrfor passing a gaseous cooling agent into the rapid cooling zone portion of the kiln chamber.

14. rlhe method of operating `an open fired tunnel kiln which consists in supplying heating gases to the kiln chamber at the opposite ends of an .intermediate section of the kiln lchamber and moving the heating gases so supplied through the kiln chamber away from said intermediate section toward the oppositeends of thekiln and introducing a gaseous cooling medium into said intermediate section.

15; The method of operatingan open fired tunnel kiln whichA consists in supply-y ing heating gases to the kiln chamber at the opposite ends of anintermediate section of the'kniln chamber and moving the heating gases so supplied through the kiln chamber away from said intermediate section toward the ends of Athe kiln and introducing a gaseous cooling medium into said intermediate sectiongof the kiln chamber at a temperature intermediate the temperature of the atmosphere andthe temperature in said intermediate section.A

16. in a continuous tunnel kiln, the com.v

ice

een

a heating fluid to flow in the. opposite dibination with the kiln chamber and means rection through said intermediate kiln por-` for supplying heat to one end portion and tion. for abstraeting heat from the opposite end A15 17. In a continuous tunnel kiln, the comportion of the chamber, of means for op- 5. bination with the kiln chamber and means tionally supplying heat to or abstracting it for supplying heat to a heating up zone or from -an intermediate portion of the kiln section of the kiln Chamber," of means for chamber as desired.

optionally supplying heat to 0r abstracting v Signed at Cleveland in the county of- 20 it from an adjacent cooling zone or section lCuyahoga and State of Ohio this'231'd day 10 of the kiln as required to regulate the tem of July A. D., 1923.

perature therein. f 18.' In a continuous tunnel kiln, the comi PHILIP DI-IUC DRESSLER. 

